1. Field of the Invention
The present invention relates to a photometric apparatus and an automatic analyzer.
2. Description of the Related Art
Conventional automatic analyzers use photometric apparatuses that measure, using light of different wavelengths depending on what is to be measured, a reaction liquid in which a reagent and a test liquid react. An example of such automatic analyzers is a pre-spectroscopic automatic analyzer (e.g., see Japanese Utility Model Application Laid-open No. H6-19079) in which light sources respectively emitting light of different wavelengths and light-receiving devices are located opposing each other and along an arrangement direction. The center angles among the light sources or light-receiving devices are the same as the center angle among reaction vessels set on a cuvette wheel. The automatic analyzer intermittently rotates the cuvette wheel to transfer the reaction vessels, which then cut across light axes of light of different wavelengths emitted from the light sources. On the basis of the light absorbance of the reaction liquid, the automatic analyzer analyzes a constituent concentration and the like of a specimen.
In the pre-spectroscopic automatic analyzer disclosed in Japanese Utility Model Application Laid-open No. H6-19079, light is dispersed into light of different wavelengths and then emitted from the light sources. When the automatic analyzer in Japanese Utility Model Application Laid-open No. H6-19079 intermittently rotates the cuvette wheel, a problem occurs in that some reaction vessels cut across only light axes of light of different wavelengths emitted from part of light sources. For example, in a photometric apparatus shown in FIG. 9, light sources L1-L5 respectively emit light (of wavelengths λ1-λ5), and light transmitted through a liquid contained in a reaction vessel C is received by the light-receiving devices R1-R5.
In the photometric apparatus shown in FIG. 9, suppose, for convenience of the description, that Nos. 1-27 are attached to reaction vessels C and arranged in the counterclockwise direction, that the 27 reaction vessels C are arranged on a cuvette wheel H, and that one intermittent rotation transfers a portion of the reaction vessels, i.e., seven reaction vessels C. Considering the rotation direction of the cuvette wheel H, No. 1 reaction vessel C is positioned right in front of the light source L1 and the light-receiving device R1. FIG. 10 is a schematic diagram in which positions of the light sources L1-L5, the light-receiving devices R1-R5, and the reaction vessels C before the cuvette wheel H is rotated are viewed from the inside of the cuvette wheel H, and the reaction vessels C are arranged in a straight line.
To measure optical characteristics of liquids contained in the reaction vessels C, the cuvette wheel H in a state in FIG. 10 is rotated by one intermittent rotation in the clockwise direction, as represented by the arrow. Then, the reaction vessels C arranged on the cuvette wheel H are transferred to the right by seven units as shown in FIG. 11. As a result, Nos. 1-3 reaction vessels C cross the light sources L1-L5 so that the measurement of the optical characteristics of the liquids is completed with light of different wavelengths (wavelength λ1-λ5). Nos. 4-7 reaction vessels C, however, cross only some light sources emitting part of different wavelengths, and the measurement of the optical characteristics of the liquids may not be completed.
For example, when the light sources L1 and L2 and the light-receiving devices R1 and R2 are used to take a measurement, the measurement of the optical characteristics is completed for Nos. 1-6 reaction vessels C but not completed for No. 7 reaction vessel C as shown in FIG. 11.